Postage meters are devices for dispensing value in the form of postage printed on a mail piece such as an envelope. The term postage meter also includes other similar meters such as parcel post meters. Meters of this type print and account for postage stored in the meter. Mechanisms are provided in the meter to select a particular value of postage to be printed on a mail piece.
Postage meters have been developed with electronic accounting systems. Postage meter systems of this type are disclosed in U.S. Pat. No. 3,978,457 for Microcomputerized Electronic Postage Meter System and in U.S. Pat. No. 3,938,095 for Computer Responsive Postage Meter. With the development of electronic postage meters, it has been desired to develop value selection mechanisms which cooperate with the electronic circuits in a manner to enhance the capabilities of the postage meter.
Postage meter printing systems suitable for use with electronic postage meters, such as those disclosed in U.S. Pat. No. 3,965,815 for Setting Mechanism for a Postage Printing Device and U.S. Pat. No. 4,050,374 for Meter Setting Mechanism, include a printing drum with a set of adjacent printing wheels each of which carries print characters. Each print wheel is set to position a different postage amount character for printing by an independently rotatable gear mechanism adapted to be engaged by a master gear. The master gear is rotatably mounted within a laterally movable carriage. The carriage can be moved to cause successive engagement of the master gear with independently rotatable gear mechanisms. The printing drum is energized to rotate to print postage by a drive gear within the meter. Meter printing systems of this type are often detachably mounted on a drive base. When so mounted, the postage meter drive gear meshes with a drive gear in the base. One suitable drive base is disclosed in U.S. Pat. No. 2,934,009 for Sheet Feeding and Treating. These mechanisms operate satisfactorily for their intended purposes.
It has been recognized that it may be desirable to perform a value setting operation during rotation of the printing drum. One system for accomplishing such setting is disclosed in U.S. Pat. No. 4,140,055 for Automatic Device for Value-Setting of Print Wheel in a Franking Machine. With the mechanism disclosed in the patent, however, the drum must be in rotation during the value selection. This requires that the full selection process be both operated and completed prior to each print cycle since the value selection must be operated whether or not the value of the postage to be printed changes from the proceeding print cycle. This adds wear to the mechanism. Moreover, the flexibility which is obtainable by electronic postage meters is sacrificed in that the selection mechanism cannot be operated when the print drum is at rest.